Corner bend in fibrous sheet material

ABSTRACT

A method of forming an exterior corner bend in fibrous sheet material in which a pair of parallel, overlapping, V-shaped grooves are formed across one side surface of the material so as to provide a pair of bevelled edge faces spaced apart by a triangular rib, filling the V-shaped grooves with a liquid settable rib and maintaining the sheet in its bent condition until the adhesive sets.

United States Patent [1 1 Spurdle June 24, 1975 1 CORNER BEND IN FIBROUSSHEET MATERIAL [76] Inventor: Graham David Spurdle, 675 Alpine Ct.,North Vancouver, British Columbia, Canada 22 Filed: Oct. 9, 1973 21App]. No.: 404,228

[52] US. Cl 52/631; 52/211 [51] Int. Cl. F04c 2/00 {58] Field of Search52/631, 211; 161/102, 106, 161/108 [56] References Cited UNITED STATESPATENTS 2,505,789 5/1950 Norquist 52/631 3,200,547 8/1965 Johnson 52/631X 3,517,427 6/1970 Bainter et a1. 52/631 X 3,649,398 3/1972 Keith 52/631UX 3,654,053 4/1972 Toedter 52/631 X 3,729,870 5/1973 Kualhein et a152/631 X Primary Examiner-Frank L. Abbott Assistant ExaminerCarl D.Friedman Attorney, Agent, or FirmCarver and Company [57] ABSTRACT Amethod of forming an exterior corner bend in iibrous sheet material inwhich a pair of parallel, overlapping, V-shaped grooves are formedacross one side surface of the material so as to provide a pair ofbevelled edge faces spaced apart by a triangular rib, filling theV-shaped grooves with a liquid settable rib and maintaining the sheet inits bent condition until the adhesive sets.

3 Claims, 3 Drawing Figures 1 CORNER BEND IN FIBROUS SHEET MATERIALBACKGROUND OF THE INVENTION 1. Field of the Invention v This inventionrelates to forming exterior bends in fibrous sheet material, such asplywood sheeting, for finishing trim around doorways, window easementsand the like. v

2. Prior Art Conventionally, trim around doorways and the like, hasusually been made of finished dimensioned lumber which is stained orotherwise finished to match the wall panelling or door adjacent. Withmodern prefinished door skins in which the finished side can be asuitable plastic such as vinyl or paper which can be treated to simulateany type of wood it is very difficult, if not impossible, to obtain andfinish solid wooden trim to obtain an exact match. Consequently doorwaytrim and the like, is now, in many cases, formed substrate material asthe door and which has an exterior finish which matches, exactly, thefinish of the door.

Individual members of the latter type of trim have a channelcross-section and are formed from a single finished piece of substratewhich is suitably corner bent and glued to provide the requiredstrength.

In prior art procedures for forming a corner bend a V-shaped groove iscut in the unfinished side of the piece through the various substratethicknesses up to but not through the exterior finish. The groove isthen filled with a suitable adhesive then bent to the desired anglealong the V-shaped groove and held in position until the adhesive hasset. The exterior corner bend thus formed usually presents an unbrokenexterior finish, if the finish is vinyl. With exterior finishes of afibrous nature such as paper, splitting of the finish sometimes occurs.

Furthermore an exterior corner as formed above presents a sharp edgewhich is susceptible to damage and cannot easily be repaired.

SUMMARY OF THE INVENTION The present invention provides a method forforming corner bends in sheet material of a rigid fibrous nature whichprovides a chamfered exterior corner and which is, consequently, not asreadily damaged as sharp cornered corner bends.

Furthermore, the present method of forming corner bends reducesincidences of splitting of the exterior finish particularly where thefinish material is of a fibrous nature, such as paper.

In accordance with the invention the corner bend is formed by cuttingtwo parallel, over-lapping, V-shaped grooves across the unfinished sideof the panel up to but not through the exterior finish so as to form acentral triangular rib, filling the grooves with a suitable adhesivethen bending the panel on lines coincident with the bottoms of theV-shaped grooves, and maintaining the bend until the adhesive has set.

A detailed description following, related to drawings, givesexemplification of methods according to the invention which, however, iscapable of expression in method other than those particularly describedand iilustrated.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a door jamb,trim members of which are formed in accordance with the invention.

FIG. 2 is an enlarged sectional view of a portion of a trim member priorto bending,

FIG. 3 is a sectional view illustrating a finished corner bend.

DETAILED DESCRIPTION Referring to the drawings, FIG. I is a transversesection of one side of a door jamb having a stop 1.0,jamb faces Ill and12, and side trim 13 and 14 all of which are formed of thin plywoodsheeting finished on one side which is corner bent to provide anunbroken finished surface.

The corner bends of the door stop and jamb faces are in extent, whereas,trim l3 and 14 have corner bends 15 and R6, less than 90 and cornerbends l7 and 18 which are greater than 90. The exterior corner bends areall formed in the same manner.

Referring to FIGS. 2 and 3 which show a typical corner bend and a methodof making the same, the numeral 21 designates a sheet of laminatefibrous material, for example plywood, which has an unfinished interiorsurface 22 and has a finishing veneer 23 applied, in a known manner, toits outer surface 24. The finish, can, conventionally be vinyl or paperor other known materials.

A pair of parallel, over-lapping, V-shaped grooves 25 and 26 are formedacross the interior surface 22, the apeces 27-27 extending to, but notthrough, the exterior finish 23 so as to form a central triangularlyshaped rib of wood 29 and a pair of panels 31 and 32 which have bevellededge faces 33 and 34 and which are connected only by the exteriorfinishing veneer 23. The rib, for plywood one-eighth inches inthickness, suitably, a base length of one-sixteenth inches.

The V-shaped grooves are then filled with a suitable liquid adhesive 35,for example a hot melt glue having a polyethelene or polyester base, andthe panels are then folded around fold lines represented by the apeces2'727 of the grooves and maintained in a folded condition until the gluehas set.

The apex angle and spacing of the V-shaped groove is such that when thepanels 31 and 32 are bent to the desired angle, see FIG. 3, the panelsmeet at the juncture of the bevelled end faces and the inside surfacesof the panel. It will be seen that during bending the volume of theV-shaped grooves is reduced so that ideally excess glue is squeezed outonto the inside surface of the panels. This strengthens the exteriorcorner bend thus formed.

The provision of the central rib results in a ehamfer 31 rather than asharp corner edge the deflection angle at each edge of the ehamfer beingonly one half of the corner bend angle. Due to the decreased deflectionangle and due to the softening of the veneer by the hot glue, incidencesof splitting of the finishing veneer, at the corner bend duringproduction, is markedly reduced.

Furthermore the chamfered corner can withstand, without excessivedamage, the impact of hard objects.

It is to be understood that although reference has been made to cornerbending fibrous material having exterior finishing veneer the samemethod of corner 3 4 bending can be used with plywood sheets having nofinneer and having side surfaces spaced from said bevishing veneer. Inthis case depth of the Vshaped elled end faces, grooves is only slightlyless, approximately 8/1000 e. the inner edges of said sheet portionsbeing in inChBS, than the thickness Of the Sheet material. ontact eachother and Said end faces being I Claim? non-parallel to each otherwhereby a space is de- 1. An exterior corner structure for a rigid sheetof f1 fined by Said end faces of said sheetgpomons and brous materialhaving a flexible sheet of finishing veneer on the exterior surfacethereof comprising:

a. a pair of sheet portions connected by said veneer extending unbrokenbetween the two sheet por- 10 said side surfaces of said central rib,and f. an adhesive substantially filling said space and bonded to saidend faces and said side surfaces.

2. A corner bend as claimed in claim 1 in which the tions, b. said sheetportions being at substantially a right adheslve a hol melt glueangle toh other 3. A corner bend as claimed in claim 1 in which the said heetortion h i b ll d d f triangularly shaped rib has a base length ofsubstand. a central rib of triangular cross-section disposed tiallyOne-sixteenth inches.

between said end faces and connected to said ve-

1. An exterior corner structure for a rigid sheet of fibrous materialhaving a flexible sheet of finishing veneer on the exterior surfacethereof comprising: a. a pair of sheet portions connected by said veneerextending unbroken between the two sheet portions, b. said sheetportions being at substantially a right angle to each other, c. saidsheet portions having bevelled end faces, d. a central rib of triangularcross-section disposed between said end faces and connected to saidveneer and having side surfaces spaced from said bevelled end faces, e.the inner edges of said sheet portions being in conTact with each otherand said end faces being non-parallel to each other whereby a space isdefined by said end faces of said sheet portions and said side surfacesof said central rib, and f. an adhesive substantially filling said spaceand bonded to said end faces and said side surfaces.
 2. A corner bend asclaimed in claim 1 in which the adhesive is a hot melt glue.
 3. A cornerbend as claimed in claim 1 in which the triangularly shaped rib has abase length of substantially one-sixteenth inches.